Collections

Swift provides three primary collection types: Array, Set, and Dictionary. All three are generic, type-safe, and implemented as value types with copy-on-write optimisation.

---

Arrays

An array is an ordered collection of elements of the same type:

// Creating arrays
var fruits: [String] = ["Apple", "Banana", "Cherry"]
var numbers = [1, 2, 3, 4, 5]        // inferred as [Int]
var empty: [Double] = []
var repeated = Array(repeating: 0, count: 5)  // [0, 0, 0, 0, 0]

Accessing and Modifying

// Accessing
let first = fruits[0]            // "Apple"
let last = fruits.last           // Optional("Cherry")
let count = fruits.count         // 3
let isEmpty = fruits.isEmpty     // false

// Modifying
fruits.append("Date")            // ["Apple", "Banana", "Cherry", "Date"]
fruits.insert("Elderberry", at: 1)
fruits.remove(at: 0)
fruits[0] = "Blueberry"

// Safe access with bounds checking
if let item = fruits.first {
    print("First fruit: \(item)")
}

Iterating

for fruit in fruits {
    print(fruit)
}

for (index, fruit) in fruits.enumerated() {
    print("\(index): \(fruit)")
}

Functional Operations

let numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]